Fluid titration system
A fluid titration system has an optical sensor, a physiological monitor, a titration controller and an infusion device. The optical sensor transmits multiple wavelengths of light into a tissue site of a person and detects the optical radiation after attenuation by pulsatile blood flowing within the tissue site. The physiological monitor receives a resulting sensor signal and derives a plethysmograph that corresponds to the pulsatile blood flow. The monitor also calculates a plethysmograph variability measure that is responsive to changes in perfusion at the tissue site. A titration controller generates a fluid control output according to the variability measure. The infusion device administers a liquid solution via an intravenous (IV) connection to the person according to the fluid control output so as to regulate at least one of a fluid flow start, rate and stop.
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The present application claims priority benefit under 35 U.S.C. §119(e) from U.S. Provisional Application No. 60/993,584, filed Sep. 13, 2007, entitled “Fluid Titration System,” which is incorporated herein by reference.
BACKGROUND OF THE INVENTIONPulse oximeters capable of reading through motion induced noise are disclosed in at least U.S. Pat. Nos. 6,770,028, 6,658,276, 6,650,917, 6,157,850, 6,002,952, 5,769,785, and 5,758,644; low noise pulse oximetry sensors are disclosed in at least U.S. Pat. Nos. 6,088,607 and 5,782,757; all of which are assigned to Masimo Corporation, Irvine, Calif. (“Masimo”) and are incorporated by reference herein.
Physiological monitors and corresponding multiple wavelength optical sensors are described in at least U.S. patent application Ser. No. 11/367,013, filed Mar. 1, 2006 and entitled Multiple Wavelength Sensor Emitters and U.S. patent application Ser. No. 11/366,208, filed Mar. 1, 2006 and entitled Noninvasive Multi-Parameter Patient Monitor, both assigned to Masimo Laboratories, Irvine, Calif. (Masimo Labs) and both incorporated by reference herein.
Further, physiological monitoring systems that include low noise optical sensors and pulse oximetry monitors, such as any of LNOP® adhesive or reusable sensors, SofTouch™ sensors, Hi-Fi Trauma™ or Blue™ sensors; and any of Radical®, SatShare™, Rad-9™, Rad-5™, Rad-5v™ or PPO+™ Masimo SET® pulse oximeters, are all available from Masimo. Physiological monitoring systems including multiple wavelength sensors and corresponding noninvasive blood parameter monitors, such as Rainbow™ adhesive and reusable sensors and RAD-57™ and Radical-7™ monitors for measuring SpO2, pulse rate, perfusion index, signal quality, HbCO and HbMet among other parameters are also available from Masimo.
PI=AC/DC (1)
where “AC” 454 designates a peak amplitude 462 minus a valley amplitude 464 for a particular pulse and where “DC” 456 designates a peak amplitude 462 for a particular pulse. In an embodiment, an IR channel plethysmograph from a detector response to an IR wavelength LED is utilized to calculate PI. A plethysmograph variability index (PVI) is then calculated that is responsive to variations in perfusion index, as described below.
In an embodiment, PVI calculations utilize only PI values resulting from acceptable plethysmograph pulses. For example, a red channel plethysmograph responsive to a red wavelength LED is used to verify acceptable pulses in the IR channel. Physiological plethysmograph identification is disclosed in U.S. Pat. No. 7,044,918 titled Plethysmograph Pulse Recognition Processor, which is incorporated by reference herein. PVI values are calculated from a sorted and trimmed buffer representing a sliding time window of PI values. The sort orders the PI values from the minimum PI at one end of the buffer to the maximum PI at the other end of the buffer. A predetermined number of both maximum and minimum PIs are deleted from each end of the buffer and PVI is calculated as:
PVI=[(PIMAX−PIMIN)/PIMAX]×100 (2)
That is, PVI is the PI variation, expressed as a percentage of the difference between the maximum and minimum PIs remaining in the buffer. In an embodiment, a median PVI is calculated from PVIs stored in a second buffer. PVI is described in U.S. Provisional Patent App. No. 60/873,663 filed Dec. 9, 2006 titled Plethysmograph Variability Index, incorporated by reference herein. A PVI enabled physiological monitor advantageously provides a noninvasive numerical measure of hypovolemic conditions so as to titrate patient fluids.
As shown in
In an embodiment, the fluid titration process 670 triggers a control output 644 so as to enable fluid flow from the IV infusion device 540 if PVI increases above a predetermined threshold or otherwise reflects that hypovolemia may no longer be indicated for a patient 2 (
A fluid titration system has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in art will appreciate many variations and modifications.
Claims
1. A fluid titration system comprising:
- an optical sensor that transmits multiple wavelengths of optical radiation into a tissue site of a person and detects the optical radiation after attenuation by pulsatile blood flowing within the tissue site so as to generate a sensor signal responsive to the detected optical radiation;
- a physiological monitor in electrical communications with the optical sensor, the physiological monitor configured to calculate a measure of plethysmograph variability (PV) from the sensor signal; and
- an infusion device that administers a liquid solution via an intravenous (IV) connection to the person in response to the measure of PV.
2. The fluid titration system according to claim 1 further comprising a fluid titration controller, the fluid titration controller comprising:
- a PV measure input;
- a fluid control output; and
- a predetermine relationship between the PV measure input and the fluid control output,
- wherein the control output is in communication with the infusion device so as to regulate at least one of fluid flow start, rate and stop.
3. The fluid titration system according to claim 2 wherein the PV measure is responsive to changes in perfusion index (PI) over a time interval where one or more complete respiratory cycles have occurred.
4. The fluid titration system according to claim 3 further comprising:
- a digital signal processor (DSP); and
- a closed-loop fluid titration algorithm implemented in firmware executing on the DSP so as to implement the predetermined relationship.
5. The fluid titration system according to claim 4 further comprising an enclosure integrating the physiological monitor with the infusion device.
6. A fluid titration method comprising:
- deriving a plethysmograph waveform from an optical sensor attached to a person;
- determining a measure of perfusion variability corresponding to the plethysmograph waveform; and
- adjusting blood volume for the person based upon the perfusion variability metric.
7. The fluid titration method according to claim 6 wherein determining a measure of perfusion variability comprises calculating a perfusion variability index based upon a maximum perfusion measurement compared to a minimum perfusion measurement.
8. The fluid titration method according to claim 7 wherein adjusting comprises displaying an IV infusion device adjustment prompt to a care provider according to the perfusion variability index.
9. The fluid titration method according to claim 7 wherein adjusting comprises transmitting a control signal to an IV infusion device according to the perfusion variability index.
10. The fluid titration method according to claim 9 wherein the transmitting comprises at least one of:
- disabling the IV infusion device from infusing fluid when PVI is less than a first predetermined threshold; and
- enabling the IV infusion device for infusing fluid when PVI is greater than a second predetermined threshold.
11. A fluid titration system comprising:
- a sensor means for transmitting multiple wavelengths of optical radiation into a tissue site and detecting the optical radiation after attenuation by pulsatile blood flow within the tissue site;
- a physiological monitor means in communications with the sensor means for deriving a plethysmograph and calculating a measure of plethysmograph variability;
- an IV infusion device in communication with the fluid titration controller means configured to infuse a fluid into the person; and
- a titration controller means for at least partially regulating the fluid infusion in response to the measure of plethysmograph variability.
12. The fluid titration system according to claim 11 wherein the titration controller means comprises an open loop means for utilizing a care provider to adjust the IV infusion device.
13. The fluid titration system according to claim 12 wherein the open loop means comprises an indicator means for communicating infusion adjustment to a care provider.
14. The fluid titration system according to claim 11 wherein the titration controller means comprises a closed-loop means for directly controlling fluid delivery by the IV infusion device.
15. The fluid titration system according to claim 14 wherein the closed-loop means comprises an infusion control output for transmitting a control signal to the IV infusion device.
16. A fluid titration method comprising:
- deriving a plethysmograph in response to an optical sensor attached to a person, the plethysmograph having a plurality of pulses in response to the person's arterial blood flow, the pulse minima of the plethysmograph defining a baseline;
- calculating a parameter indicative of a variability of the plethysmograph;
- infusing fluid into the person via an IV; and
- regulating the infusing according to the parameter.
17. The fluid titration method according to claim 16 wherein the calculating comprises:
- determining a plurality of perfusion measures corresponding to physiologically acceptable ones of the pulses; and
- computing a perfusion variation from the perfusion measures.
18. The intravenous fluid titration method according to claim 17 wherein the infusing comprises:
- connecting an IV infusion device to the IV; and
- communicating an infusion control to the IV infusion device,
- wherein fluid flow from the IV infusion device is determined by the infusion control.
19. The intravenous fluid titration method according to claim 18 wherein the regulating comprises outputting a disabling signal on the infusion control when the variability parameter is below a predetermined threshold.
20. The intravenous fluid titration method according to claim 18 wherein the regulating comprises outputting an enabling signal on the infusion control when the parameter is above a predetermined threshold.
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Type: Grant
Filed: Sep 11, 2008
Date of Patent: Nov 1, 2011
Patent Publication Number: 20090076462
Assignee: Masimo Corporation (Irvine, CA)
Inventor: Massi E. Kiani (Laguna Niguel, CA)
Primary Examiner: Kevin C Sirmons
Assistant Examiner: Michael J Anderson
Attorney: Knobbe, Martens, Olson & Bear LLP
Application Number: 12/208,998
International Classification: A61M 5/00 (20060101); A61B 5/00 (20060101);